Injection system and method for feeding particulate to a process vessel

ABSTRACT

An injection system and method for feeding a particulate material to a process vessel, including a valve with at least one cavity adapted for receipt of a predetermined volume of particulate and a sweep stream source for providing a sweep stream having flow in a direction generally toward the valve to remove substantially all of the particulate from the cavity of the valve.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an injection system for feeding a particulatematerial to a process vessel, which in a particular embodiment couldinclude, for example, feeding consistent amounts of catalyst to apolyethylene reactor over an extended period of time.

2. Description of the Prior Art

Various systems have been proposed that provide catalysts or otherparticulates to a reactor, such as a polyethylene reactor, in measuredquantities over an extended period of time. Such systems have includedvarious combinations of valves and have utilized pressurized feed gas orsweep streams of inert gases to mobilize, or transport, the particulatefrom a particulate storage vessel to the reactor. Some systemsrepeatedly open and close a particulate feed valve to allow measureddoses of the particulate to flow from the particulate storage vesselaided only by gravity directly to the reactor, or they may utilize anintermediate chamber in which to deposit the measured doses ofparticulate prior to flushing the particulate from the intermediatechamber by use of a feed gas or sweep stream. However, such priorsystems have failed to adequately provide an efficient method ofaccurately and consistently providing the measured dose of particulateto the reactor.

Various valve designs have been utilize to improve the accuracy of theparticulate dosage. For example, rotary valves have been utilized byreplacing standard cylindrical or spherical rotors in rotary valvedevices with modified rotors having a cup-shaped cavity formed thereinfor receiving the measured particulate dose. The rotor can then berotated, or inverted, between a first, or filling, position for fillingthe cavity with particulate from the particulate storage vessel and asecond, or releasing, position for releasing the particulate into theintermediate chamber. Such prior rotary valve devices may produce lessthan exact measured doses to the reactor because amounts of theparticulates may remain inside the cup-shaped cavity after being rotatedinto the second, or releasing, position. Prior systems have attempted tominimize this problem and have included small ball bearings, plates orsprings, into the bottom of the cavity, which are intended tomechanically clear any remaining particulates from the bottom of thecavity when rotated or inverted to the releasing position. Prior systemshave proved to be costly, complicated, and difficult to maintain.

Prior systems have proved to be inadequate for providing precise,measured, doses of particulates to reactors over extended periods oftime, and have proved to be complicated and difficult to maintain.Accordingly, prior to the development of the injection system of thepresent invention, there has been no injection system for feedingparticulate to a reactor that provides efficient and consistent dosagesof particulates to a reactor over an extended period of time, and whichare simple, inexpensive to maintain, have very few moving parts, andminimize failure. Therefore, the art has sought an injection system forfeeding particulate to a reactor that provides efficient and consistentdosages of particulates to a reactor over an extended period of time,and which are simple, inexpensive to maintain, have very few movingparts, and minimize failure.

SUMMARY OF THE INVENTION

In accordance with the invention, the foregoing advantages have beenachieved through the present injection system for feeding particulate toa reactor, whereby efficient and effective dosages of particulate may beprovided to a reactor over an extended period of time.

The present invention may be directed to an injection system for feedinga particulate material to a process vessel, comprising: a valve, havingat least one cavity adapted for receipt of a predetermined volume ofparticulate, and a sweep stream source for providing a sweep streamhaving flow in a direction generally toward the valve to removesubstantially all of the particulate from the cavity of the valve. Thevalve may be a rotary valve having a rotatably disposed rotor having afirst position for receiving the predetermined volume of particulate anda second position for releasing the predetermined volume of particulate,and the rotor may have a drive mechanism disposed in engagementtherewith for rotating the rotor between the first and second position.

The present invention may further be directed to an injection system forfeeding a particulate material to a process vessel, comprising: a sweepstream source; a rotor housing having a rotor receiving chamber thereinand a sweep chamber associated with the rotor housing; a rotor,rotatably disposed within the rotor receiving chamber of the rotorhousing, the rotor having at least one cavity adapted for receipt of apredetermined volume of particulate, the rotor having a first positionfor receiving the predetermined volume of particulate and a secondposition for releasing the predetermined volume of particulate to thesweep chamber of the rotor housing, the rotor further having a drivemechanism disposed in engagement therewith for rotating the rotorbetween the first and second position; a sweep stream port disposed influid communication with the sweep chamber of the rotor housing forproviding a sweep stream to the sweep chamber of the rotor housing, thesweep stream having flow in a direction generally toward the rotor toremove particulate from the rotor cavity and to transport particulate tothe reactor.

The injection system may further comprise a sweep stream directed to asurface of the cavity of the rotor, and the cavity of the rotor may havean arcuate portion or may have an entirely arcuate shape. The injectionsystem may further comprise a drive keyway, which may be formed in therotor, and the drive mechanism may include a rotary actuator having ashaft disposed in the drive keyway of the rotor. The rotor may bespherical or it may be cylindrical. The particulate may be a catalystbut is not intended to be limited to a catalyst and the process vesselmay be a polyethylene reactor but is not intended to be limited to apolyethylene reactor.

The present invention may further be directed toward a method ofinjecting particulate into a process vessel, comprising the steps of:providing a metering device disposed between a particulate storagevessel and a sweep chamber, the metering device having a rotor with acavity formed therein, which cavity may include an arcuate portion ormay have an entirely arcuate shape; providing a sweep stream directedgenerally towards the rotor; rotating the rotor to a first position forreceiving a predetermined volume of particulate stored in theparticulate storage vessel; and rotating the rotor to a second positionfor releasing the predetermined volume of particulate to the sweepchamber, whereby the sweep stream will flush any remaining particulatematerial, which may be within the cavity formed in the rotor. The sweepstream may assist in transporting the particulates to the reactor, andthe rotor may be rotatably disposed within a rotor housing.

The injection system for feeding particulate to a reactor, when comparedwith previously proposed prior art injection systems for feedingparticulate to a reactor, has the advantages of providing efficient andeffective measured doses of particulates to a reactor over an extendedperiod of time.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings:

FIG. 1 is a schematic view of an embodiment of an injection system ofthe present invention;

FIG. 2 is a partial cross-sectional view of an embodiment of aninjection system of the present invention, showing a metering devicehaving a spherical rotor disposed in a first, or filling, position;

FIG. 3 is a partial cross-sectional view of an embodiment of aninjection system of the present invention, showing a metering devicehaving a spherical rotor disposed in a second, or releasing, position;

FIG. 4 is a partial cross-sectional view of the injection system of FIG.2, showing the metering device having a cylindrical rotor.

FIG. 5 is a partial cross-sectional view of an alternate embodiment of arotor of the present invention, showing a sweep port comprised ofmultiple apertures formed in the surface of the rotor proximate thecavity formed therein.

While the invention may be described in connection with a preferredembodiment, it will be understood that it is not intended to limit theinvention to that embodiment. On the contrary, it is intended to coverall alternatives, modifications, and equivalents as may be includedwithin the spirit and scope of the invention as defined by the appendedclaims.

DETAILED DESCRIPTION OF THE INVENTION

In a broad aspect, the present invention is directed to a method andapparatus for feeding particulate to a process vessel. The method may becarried out in connection with the apparatus, and/or the method may becarried out in connection with other apparatus. Likewise, the apparatusmay be utilized in connection with other methods. Various embodimentsand aspects of the apparatus are shown in FIGS. 1-4, where likereference numerals refer to like parts.

FIG. 1 shows in schematic form an embodiment of the present injectionsystem 10 for feeding particulate, such as a catalyst, to a processvessel, or reactor 500, which may be used in the processing ormanufacturing of polyethylene, for example. The injection system mayinclude a particulate storage vessel 100, which may be used to storeexcess amounts of the particulate 2 to be fed to the reactor 500; ametering device 200, comprising a rotary valve 205 (FIGS. 2-4), whichmay be a standard cylindrical or spherical ball valve 205 known in theart that has been modified as described further hereinbelow; anintermediate chamber 400 in which measured doses of particulate 2 may beinitially deposited prior to being transported by, for example, theforce of gravity to the reactor 500. Sweep stream source 300 may beprovided and disposed in fluid communication with sweep chamber 204(FIGS. 2-4) and the intermediate chamber 400 by use of conduit 310disposed in fluid communication with sweep stream port 320, which isprovided in fluid communication with sweep chamber 204 (FIGS. 2-4) andintermediate chamber 400. The sweep chamber 204 may be utilized as theintermediate chamber 400 or a separate sweep chamber 204 andintermediate chamber 400 may be used, as shown in FIGS. 2-4. Sweepstream port 320 may preferably be configured to direct the flow of thesweep stream, represented by solid arrows 319 (FIGS. 2-4), toward themetering device 200 to assist in releasing the particulate 2 from cavity209 (FIGS. 2-4) formed in metering device 200, as hereinafter described.As described more fully hereinbelow, in operation, metering device 200will oscillate, or reciprocate, between a first position (FIG. 2) forfilling the metering device with a measured dosage of particulate 2 fromthe volume of particulate 2 stored in the particulate storage vessel 100and a second position (FIG. 3) for releasing the measured dosage ofparticulate 2 into the sweep chamber 204 or intermediate chamber 400.

While the metering device 200 is in the second position (FIG. 3), thepressurized sweep stream, provided by the sweep stream source 300through sweep stream port 320 into the sweep chamber 204 or intermediatechamber 400, is directed toward the metering device 200 to facilitateremoval of particulate 2 from the metering device 200. The sweep streammay be any material suitable for use as a sweep stream, but ispreferably an inert gas such as nitrogen, which may be pressurized at arelatively high pressure to ensure efficient and complete removal of theparticulate 2 from within cavity 209, and may be: directed in thegeneral direction of the cavity 209; directed directly toward the cavity209; or directed at an appropriate angle toward an appropriate surface207 of cavity 209.

Cavity 209 of rotor 208 may include an arcuate portion such as arcuateportion 203 shown in FIG. 2 or cavity 209 of rotor 208 may have anentirely arcuate shape, as shown in FIG. 5, to facilitate efficientremoval of particulate 2 from within cavity 209. The arcuate shape ofcavity 209 and the flushing action of the sweep stream facilitateefficient removal of particulate 2 from within cavity 209. The sweepstream may be provided in a continuous flow or it may be provided inintermittent bursts timed by suitable control means known in the art toefficiently remove particulate 2 from cavity 209. The particulate 2 maythen be transported through the intermediate chamber 400 by gravity orother forces into the reactor 500. In addition to facilitating removalof particulate 2 from cavity 209, the sweep stream may also assist intransporting particulate 2 through reactor conduit 410 to reactor 500.

Referring now to FIG. 2, a metering device 200 of the injection system10 of the present invention is shown in the first, or filling, position.Metering device 200 may preferably include a rotor housing 202 having asweep chamber 204 and a rotor receiving chamber 206 therein. The rotor208 may be rotatably disposed within the rotor receiving chamber 206 ofthe rotor housing 202 and may have a cavity 209 formed therein, whichpreferably may be cup-shaped or bowl-shaped, having an arcuate portion203. Those skilled in the art will recognize that various shapes andsizes of the various components could be selected depending upon thecharacteristics of the particular particulate 2 being used, the desiredinjection rate, and other factors in a given application, including thesize of the surrounding catalyst injection system components, thevelocity and characteristics of the sweep stream material, and theamount of time that the metering device spends in each position.Although the preferred embodiment may be described in connection with aspherical rotor 208, comprising a modified ball valve having a cavitytherein, the rotor design is not limited to a spherical rotor and mayalso be a cylindrical rotor 208, as shown in FIG. 4. In addition, therotor design of the present invention is not limited to having a singlecavity 209 or to a cavity 209 of any particular size or shape; however,in a preferred embodiment, the rotor 208 preferably has one cavity 209,having a relatively large opening and a relatively shallow depth and ispartially or completely arcuate.

Still with reference to FIG. 2, the metering device 200 of the injectionsystem 10 of the present invention is shown rotatably disposed withinthe rotor receiving chamber 206 of the rotor housing 202. The rotor 208is shown having at least one generally cup-shaped cavity 209 portionformed therein that is shaped and sized to receive a predeterminedvolume of particulate 2. The rotor 208 is shown in its first positionfor receiving the predetermined volume of particulate 2 stored in theparticulate storage vessel 100. The rotor 208 further includes a drivekeyway 210 formed therein for receiving the shaft 200 of a drivemechanism, or actuator 212, that is disposed in operative engagementtherewith for rotating the rotor 208 between the first position of FIG.2 and a second position as shown in FIG. 3. In a preferred embodiment,the rotor 208 of metering device 200 may be a ball valve 205 of the typeidentified in the art as a Whitey 1/2" S60P ball valve having a 180°actuator, the valve 205 having been modified by discarding its standardball and replacing the ball with a spherical rotor having a cavity 209,as shown in FIGS. 2-3.

Now with reference to FIG. 3, the metering device 200 of the injectionsystem 10 of the present invention is shown in its second position forreleasing the predetermined volume of particulate 2 stored in cavity 209of the rotor into the sweep chamber 204, or intermediate chamber 400,for transport to the reactor 500 by gravity, or other motive force,which may be assisted by the sweep stream represented by solid arrows319. Sweep stream port 320 is shown disposed through the rotor housing202 directed at the cavity 209 in the rotor 208. The sweep streamrepresented by solid arrows 319 is provided by sweep stream source 300through sweep stream conduit 310 and enters rotor housing 202 in adirection generally toward rotor 208. It should be apparent to thoseskilled in the art that other methods of directing the sweep streamtoward rotor 208 can be utilized. Accordingly, the injection system 10of the present invention is not to be limited to a sweep port 320provided in the rotor housing 202, but should include other embodimentsapparent to those skilled in the art for directing the sweep streamtoward the rotor 208. For example, the sweep stream may be directedtoward the rotor 208 by means of a hose provided within reactor conduit410 and running along the interior of reactor conduit 410 having an enddisposed proximate rotor 208. In addition, as shown in FIG. 5, meteringdevice 200 may include a port formed within rotor 208 that may apply asweep stream from apertures formed in the surface of the cavity tofurther eject particulate from within the cavity. The aperture wouldthen be in fluid communication with the sweep stream source by way of aconduit disposed through the shaft of the actuator. Single or multiplesweep streams may also be used in a particular embodiment.

Now with reference to FIGS. 2 and 3, in operation of a particularembodiment, rotor 208 is directed upwards in the first, or receiving,position (FIG. 2) to allow gravity filling of particulate 2 fromparticulate storage vessel 100. Shaft 211 of actuator 212, disposed inengagement with drive keyway 210 then rotates 180°, causing rotor 208 toalso rotate 180° to the second, or releasing, position (FIG. 3) wherethe particulate 2 is allowed to fall out of cavity 209 formed in rotor208 by gravity. The sweep stream represented by solid arrows 319,directed towards cavity 209 formed in rotor 208, flushes any additionalparticulate 2 that would otherwise remain in the cavity 209 formed inrotor 208 after rotating rotor 208 180°. In addition to sweeping theparticulate 2 from the cavity 209 of rotor 208, the sweep stream alsofacilitates transfer of the particulate 2 from the sweep chamber 204 orintermediate chamber 400 to the destination vessel, or reactor 500.Actuator 212 then rotates rotor 208 again 180° and the process repeatsto provide a consistent and accurate feed of catalyst or otherparticulate 2 to the reactor 500 over an extended period of time.

It is to be understood that the invention is not limited to the exactdetails of construction, operation, exact materials, or embodimentsshown and described, as obvious modifications and equivalents will beapparent to one skilled in the art. For example, actuator 212 mayreciprocate between 180° from the first to the second position and backor it may continually rotate through the first and second positions,depending on the actuator type used. In addition, the first and secondpositions of the rotor may be separated by an angle less than 180° suchas, for example, where the cavity and rotor housing may be adapted sothat the gravity feeding of the particulate is assisted by or replacedwith some external force and/or where the stream sweep stream alone orsome other force other than gravity assists in the removal ofparticulate from the cavity of the rotor. In addition, even wheregravity and the sweep stream alone facilitate removal of the particulatefrom the cavity of the rotor, a particular configuration of the cavity,and rotor, and rotor housing could be used so that an angle less than180° would separate the first and second positions.

Accordingly, the invention is therefore to be limited only by the scopeof the appended claims.

What is claimed is:
 1. An injection system for feeding a particulatematerial to a process vessel, comprising:a valve, having at least onecavity adapted for receipt of a predetermined volume of particulate, anda sweep stream source for providing a sweep stream having flow in adirection generally toward the valve to remove substantially all of theparticulate from the cavity of the valve.
 2. The injection system ofclaim 1, wherein the valve is a rotary valve having a rotatably disposedrotor having a first position for receiving the predetermined volume ofparticulate and a second position for releasing the predetermined volumeof particulate.
 3. The injection system of claim 2, wherein the rotorhas a drive mechanism disposed in engagement therewith for rotating therotor between the first and second position.
 4. An injection system forfeeding a particulate material to a process vessel, comprising:a sweepstream source; a rotor housing having a rotor receiving chamber thereinand a sweep chamber associated with the rotor housing; a rotor,rotatably disposed within the rotor receiving chamber of the rotorhousing, the rotor having at least one cavity adapted for receipt of apredetermined volume of particulate,the rotor having a first positionfor receiving the predetermined volume of particulate and a secondposition for releasing the predetermined volume of particulate to thesweep chamber of the rotor housing, the rotor further having a drivemechanism disposed in engagement therewith for rotating the rotorbetween the first and second position; a sweep stream port disposed influid communication with the sweep chamber of the rotor housing forproviding a sweep stream to the sweep chamber of the rotor housing, thesweep stream having flow in a direction generally towards the rotor toremove particulate from the rotor cavity.
 5. The injection system ofclaim 4, wherein the sweep stream is directed to a surface of the cavityof the rotor.
 6. The injection system of claim 4, wherein the cavitysurface has an arcuate portion.
 7. The injection system of claim 4,wherein the cavity surface has an entirely arcuate shape.
 8. Theinjection system of claim 4, wherein the rotor includes a drive keywayand the drive mechanism includes a rotary actuator having a shaftdisposed in the drive keyway of the rotor.
 9. The injection system ofclaim 4, wherein the rotor is spherical.
 10. The injection system ofclaim 4, wherein the rotor is cylindrical.
 11. The injection system ofclaim 4, wherein the particulate material is a catalyst and the processvessel is a reactor.
 12. The injection system of claim 11, wherein thereactor is a polyethylene reactor.
 13. A method of injecting particulateinto a process vessel, comprising the steps of:providing a meteringdevice disposed between a particulate storage vessel and a sweepchamber, the metering device having a rotor with a cavity formedtherein; providing a sweep stream directed generally toward the rotor;rotating the rotor to a first position for receiving a predeterminedvolume of particulate stored in the particulate storage vessel; androtating the rotor to a second position for releasing the predeterminedvolume of particulate to the sweep chamber,whereby the sweep stream willremove substantially all of the particulate material from the cavityformed in the rotor when the rotor is in the second position.